Session 8 - The Intestines Flashcards
What are teniae coli?
- thickened bands of smooth muscle
- run length of LI
- tonic contractions allow regions which they are associate to become baggy forming Haustra
Name some things which all sections of the SI secrete.
- Protease/carbohydrase enzymes
- Secretin
- Gastrin
- CCK
Where is iron absorbed in the GI tract?
The duodenum
What is absorbed in the jejunum?
- FAs
- Vitamins and Electrolytes
- Minerals
- Water
How are amylopectin molecules digested and eventually absorbed?
- Broken down by amylase into alpha-limit dextrins
- then in the brush border broken down into maltose by isomaltase
- The Maltose is then broken down to glucose by Maltase
- glucose is then absorbed through the SGLT1 channel
How is trypsinogen activated and why is it so important in protein digestion?
Proteolytically cleaved by enteropeptidase into trypsin
Trypsin then activates all of the other proteases allowing proteins and peptides to be digested into aa’s and small peptides which can then be absorbed
Why is it important that neonates can absorb whole proteins?
Ensures that passive immunity can be passed on from the mother through the absorption of IgA
What is the general mechanism for the absorption of amino acids?
Use a sodium/aa co-transporter which works by using the sodium gradient set up by the Na-K-ATPase
How are salts and hence water absorbed by the GI tract?
- sodium taken up via diffusion into cells
- then actively pumped across basolateral membrane
- chloride ions follow
- creates osmotic gradient for absorption of water
What is Pernicious anaemia and how might it be caused?
Anaemia caused by the failure to absorb Vit B12. It may occur due to damage to the stomach preventing secretion of intrinsic factor or due to Chrohn’s disease or if terminal ileum has been removed
Explain the basis of Oral rehydration therapy
Contains both sodium and glucose
Large amounts of sodium in GI cause large amounts of absorption coupled with glucose absorption. This creates a massive osmotic gradient for the absorption of water
How does segmentation allow effective absorption?
- SI segmented into different regions with different pacemakers
- pacemakers cause contraction at lowering amounts going down GI
- as chyme is moved proximal->distal it reaches a contracted region so moves back d->p, this mixes contents and slows progression down GI.
Describe Mass movement
Infrequent peristaltic waves propel colonic contents from transverse to descending colon.
Induces the urge to defecate
Describe the mechanism of defecation
Following mass movement, pressure receptors in the rectum sense increased pressure.
This causes the internal sphincter to relax. The external sphincter is under voluntary control and when this is relaxed, intra-ab pressure will rise and faeces will be expelled
What is the difference between UC and CD in terms of where they effect?
UC is colorectal
CD can occur anywhere in GI
